A pirate gang that launched an abortive attack on a second US ship loaded with food aid has vowed to single out American vessels with the intention to kill their crews.

U.S. Secretary of State Hillary Rodham Clinton speaks about piracy and Somalia, Wednesday, April 15, 2009, at the State Department in Washington. [Manuel Balce Ceneta/AP Photo]

The US wants to take the war against pirates to their bases in Somalia, a strategy authorized months ago by the UN.

It's another attack on a US ship attempted revenge after the US Navy killed three pirates on Sunday while freeing a hijacked American sea captain.

On Tuesday, pirates launched an attack on "Liberty Sunday", which carries food aid for the UN World Food Program, and a crew of 20 Americans.

The pirates fired at the ship with rocket-propelled grenades and automatic weapons.

But the American crew blockaded themselves in the engine room. Later, the crew escaped and headed to Kenya under US Navy guard.

US Secretary of State Hillary Rodham Clinton said on Wednesday, the US State Department will work with shippers and insurers to improve their defenses against pirates. It's part of the US's diplomatic initiative to thwart attacks on commercial ships off the Somali coast.

Hillary Rodham Clinton, US Secretary of State, said, "You have to go after the land bases. We have a pretty good idea where the land bases are. And we want to know what the Somali government, what tribal leaders, who perhaps would not like to have the international community bearing down on them, would be willing to do to rid their territory of these pirate bases."

There has been a recent surge in pirate attacks in the region.

US President Barack Obama has vowed to take action against the banditry. And five pirates have been killed in French and US hostage rescues. But this hasn't stopped sea-going gangs from seizing four vessels and more than 75 hostages since Sunday's dramatic rescue of the American captain.

In all, Somali Pirates have attacked 79 ships this year and successfully hijacked a quarter of them.

Currently, they are holding over 280 sailors on 15 ships. And at least 76 of those sailors were captured in the last few days.

(CCTV April 16, 2009)